Fire extinguishing foams containing finely dispersed silica

ABSTRACT

The fire extinguishing characteristics of fire extinguishing agents, such as foam forming liquids, containing surface active substances, are enhanced by incorporating into the agent about 1 to 10% by weight of finely dispersed silica. Particularly advantageous results are obtained if the silica is present in fire extinguishing liquids in colloidally dissolved form.

United States Patent Fink et al.

[151 3,655,554 [451 Apr. 11, 1972 [54] FIRE EXTINGUISHING FOAMS CONTAINING FINELY DISPERSED SILICA [72] Inventors: Hans-Ferdi Fink; Gotz Koerner; Gerd Rossmy; Gunter Schmidt, all of Essen, Germany [73] Assignee: Th. Goldschmidt A.-G., Essen, Germany [22] Filed: Sept. 29, 1970 [21] Appl. No.: 76,602

[30] Foreign Application Priority Data Oct. 9, 1969 Germany ..P 19 50 856.6

[52] US. Cl. ..252/3, 169/1 A, 252/805, 252/307, 252/351 [51] Int. Cl. ..A62d 1/00, A620 1/12 [58] FieldofSearch ..252/3,8.05,35l,307,6.5, 252/2, 61, 350, 313 S; 260/25 L, 2.5 AG; 169/1 A Primary Examiner-John T. Goolkasian Assistant ExaminerD. J. Fritsch Att0rney-McGlew and Toren [57] ABSTRACT The fire extinguishing characteristics of fire extinguishing agents, such as foam forming liquids, containing surface active substances, are enhanced by incorporating into the agent about 1 to 10% by weight of finely dispersed silica. Particularly advantageous results are obtained if the silica is present in fire extinguishing liquids in colloidally dissolved form.

5 Claims, No Drawings FIRE EXTINGUISIIING FOAMS CONTAINING F INELY DISPERSED SILICA CROSS REFERENCE TO PRIOR DISCLOSURE This invention corresponds to Disclosure Document 000795, filed on Oct. 27, 1969.

FIELD OF INVENTION The invention relates to liquid systems containing surface active substances which are suitable for forming fire combatting and extinguishing foams.

BACKGROUND INFORMATION AND PRIOR ART As is generally known, fires, particularly fires of fuels and propellants, are combatted by spraying foam in the form of continuous coats or coverings. Such foam blankets are also suitable for preventing the initial formation of fires.

The required foam is customarily obtained by foaming aqueous solutions of foam forming substances. The solutions sometimes also contain foam stabilizers. Suitable prior art foaming agents for such purposes are often times prepared from proteins. For this purpose, it is thus known to use keratins, albumins, seed flour, and similar protein containing substances which are modified by hydrolysis and stabilized with certain preselected metal salts.

However, as is well known in the art, foaming agents produced from protein hydrolysates cannot successfully be used for combatting certain types of fires. Thus, for example, such foaming agents are not suitable for fighting fuel fires or fires of polar substances such as, for example, alcohol fires.

A further drawback of these known foaming agents resides in the fact that they are incompatible with dry fire extinguishing powders which are customarily used simultaneously, particularly if the powders have silicon containing surfaces.

It has also recently been suggested to employ foaming agents which are water soluble, ionogenic derivatives of fluorocarbonor fluorosulfonic acids. Foaming agents or concentrates of this kind have been described, for example, in German Pat. No. 1,216,116. However, also the latter type of prior art foaming agents is not fully satisfactory. It has thus been found that foaming agents of the indicated kind do not readily form stable aqueous foams of high expansion rate.

More recently, relatively satisfactory foams have been proposed by foaming fire fighting foam concentrates which contain compounds of the general formula (11F; CF;

In this formula, a is a number of from one to three, X is hydrogen or Y, while Y is a hydrophilading group, particularly polyethyleneglycol or a group containing an aminoxide -or ammonium salt group. It has also been suggested to produce fire fighting foams of desirable characteristics by employing foam concentrates which contain from to 100% by weight of a water soluble, surface active organosilicon compound (see U.S. Pat. application Ser. No. 865,171, filed on Oct. 9, 1969).

SUMMARY OF THE INVENTION It is a primary object of the invention to provide a liquid foaming agent capable of being foamed into stable foams of superior characteristics.

Another object of the invention is to provide a liquid foaming agent system which contains an ingredient which considerably enhances the fire fighting characteristics of the foam and whose beneficial effect is essentially independent from the nature of the foam forming substances proper.

Briefly and in accordance with the invention, it has not surprisingly been found that superior fire fighting foams are obtained from aqueous fire fighting systems, if the aqueous system contains between about 1 to 10% by weight of finely dispersed silica (SiO Particularly advantageous results are obtained if the silica is in colloidally dissolved form. Such colloidally dissolved silica contains as a rule a certain amount of OH-groups which impart to the system hydrophilic characteristics to a desirable extent.

A most surprising feature of the present invention is that the silica can be beneficially incorporated in a large variety of aqueous fire fighting systems without affecting the foam forming substance or substances per se. The silica is thus essentially inert to the foam forming substance and does not negatively affect the foaming action but rather acts synergistically so as to impart the foam with desirable characteristics which would be absent in the absence of the silica. In this context it is most surprising that the fire extinguishing effect of the silica is es sentially independent from the nature of the particular foam forming agent used in the system. The same applies to systems which contain foam stabilizers. It follows that the fire combatting characteristics of foams can be successfully enhanced by the addition of the silica, irrespective of the nature of the foaming agent. Thus, whether the foaming agent proper is a protein hydrolysate or a fluorine containing surface active agent is irrelevant, since in both cases the addition of the silica significantly increases the fire combatting characteristics. Experiments, however, have indicated that particularly good results are obtained if the foaming agent proper is an organosilicon surfactant. The presence of the silica in the system not only enhances the fire fighting characteristics but also significantly increases the foam stability, whereby the so-called half value time is considerably increased.

Foams produced from the inventive aqueous foaming systems are more economical since with a given amount of foam larger burning areas can be combatted than was possible with prior art foams devoid of silica. In addition, the fires are extinguished more rapidly.

In the event that relatively small amounts of silica are to be used, these may be directly added to the aqueous foam concentrates. However, it is also feasible to add the silica in powder form during the foaming of the foaming agent proper.

Further, tests have indicated that the foaming agent and/or foam stabilizer may be mixed with finely dispersed silica in dry form, whereby a powder is obtained which is then added to water for forming the foam. It will be appreciated that a foam forming agent in dry form which contains the silica incorporated therein, can be stored more economically than a liquid concentrate.

The invention will now be described by several examples, it being understood that these examples are given by way of illustration and not by way of limitation and that many changes may be effected without affecting in any way the scope and spirit of the invention as recited in the appended claims.

The superior characteristics of the silica containing fire fighting foams are illustrated by the following examples:

EXAMPLE 1 To test the expansion rate and foam stability of the fire extinguishing foams, the so-called impact foam test was em ployed. A detailed description of the impact foam test is contained, for example, in the book by E. Manegold: Schaum, Strassenbau, Chemie and Technik-Verlagsgesellschaft m.b.H., Heidelberg, 1953, pages 97 and 98. In performing the test, a measuring cylinder with a diameter of 5.4 cm was used. The disc, used for the impact foam test, had a diameter of 5 cm and contained 87 holes with a diameter of 1 mm for each hole. The material to be foamed was filled into the measuring cylinder to a level of 3 cm and was thereafter foamed by moving the disc up and down for 40 times. The results which were obtained are tabulated in the following Tables.

The abbreviation HVT in the Tables stands for half value time and indicates the time period which passed until an amount of liquid had been reformed which corresponded to one half of the original amount. The height of the foam was measured in millimeter.

The foam produced according to the impact foam test as described was moreover used for combatting and extinguishing fires of supergasoline according to two different methods. In the first method (I I ccm of these liquids were in each case fed to a pot of a diameter of 14.5 cm. The liquids were then ignited and after a burning time of 2 minutes, the extinguishing or fire combatting procedure was initiated. This method I was also used in some instances for combatting ethanol fires. According to the second method (II), 1000 ml of the combustible liquid were in each case fed into a high rectangular tub of a base surface of l l X I8 cm. The tub was provided with an inlet pipe below the liquid level through which pipe the fire fighting foam, after ignition of the liquid and a combustion time of 2 minutes, was pressed towards the burning surface. The extinction time was the time interval between the feeding of the foam towards the burning surface and the extinction of the flame. This test serves the purpose to imitate conditions which often times occur in the fire com- The formulation numbers indicated by are comparison tests in which no silica was used.

In formulations l 17, the substances were dissolved in water in the indicated sequence. In formulation 18, a tenside containing powder was dispersed in water.

TABLE 4 Foaming characteristics and extinction time (super gasoline), Method 1 batting of storage tank fires. This is so because it is desirable to Formulw Half value Expansion Extinction time extinguish storage tank fires by pass1ng the foam through the tion No. time (min. rate (seconds) tank content and forcing it towards the liquid surface, thereby to extinguish the fire. This fire combatting procedure poses particularly high requirements on the fire extinguishing foam, 1 189 since, during the passage of the foam through the combustible 5 3,33,, 3 :2: liquid, on the one hand, the stability of the foam should not 4 decrease, while, on the other hand, larger quantities of com- 5 2000" 10 15.0 bustible liquid should not be carried along towards the burn- 6 in Surface 7 1 hour 9.5 18.6 g 8 1 hour 9 16.] TABLE 1 DESIGNATION 0F TENSIDES EMPLOYED 5 Z Tenside Chemical structure It 11'00" 7 28.l 12 5'45" 3 36.0 A (3H2 13 5 hour 3 27.0 (CHahSiO s o 14 7'02" 8 45.6 15 1356' s 30.9 2)a 3 I6 5'14" 75 38.4 17 21'00" 7 305 I8 30'00" 9 13.6

(CH2 H2 )2, 1H G SKCHOS e In each case, 70 ml of l1qu1d were foamed and used for fire HN(CHgCH20)2, 4H fi ht. l

g mg. On y in tests 12 and 13 (protein foam concentrate) 2 2 )2r 1H 210 ml of liquid were used due to the low expansion rate. TAB

LE 5 (CHzOaSiO l-O- [(C3H6o)2 Extinction Time (ethanol) Method 1 SHOE: Formulation Extinction time (C2II4O)13CH3] No. (seconds) g, (sxiigimvlrciallyli ayfailable protein [0am concentrate.

.0 um aury su ate. A A E Sodiumlaurylethersulfate. (I) docflnotemngulsh 7 9.6 TABLE 2 a 13.1

. l 18 11.2 Des1gnat1on of S1l1ca Employed Oxide Chemical Designation 85g nlilligffoam were used in each case for the fire P solid, pyrogcnicully produced SiO in powder form g with 200 m*/g surface L colloidal solution of SiO in water, concentration TABLE 6 Extmctton T1me (super gasollne), Method II TABLE 3 Formulations for Foaming Tests Formulation Extinction time No. (seconds) Tenside Colloidal Oxide No. Type Amount Type Amount weight 7r weight 7: l 1 2 26.5 3 21.3 1 A z 4 33.9 2 A 2 L 1 5 27.1 3 A 2 L 10 6 18.3 4 A 2 P 1 7 23.4 5 A 2 P 3 8 3; o A 2 P 7 9 33.0 7 A 2 P 4 I2 does not extinguish s A 1.5 P 4 13 57.0 9 A 0.5 P 4 I4 does not extinguish III I/ In each case, 70 ml of liquid were foamed and used for fire fighting. Only in formulations l2 and 13 210 ml of liquid were used.

being foamed into a fire fighting foam, the improvement which comprises that the aqueous composition contains between about I to 10% of finely dispersed silica.

3. The improvement as claimed in claim 2, wherein said silica is colloidally dissolved in the water.

4. The improvement as claimed in claim 3, wherein said silica contains OH-groups.

5. In a method of combatting fire, wherein a liquid containing surface active substance is foamed and the foam is applied to the fire, the improvement which comprises that about 1 10 percent by weight of silica in fine particle form is added to the liquid or the foam.

UNITTED STATES PATENT oTTTcT QIER ETWLQATE @F @QRREUHQN Patent No. 3,655,,554 Dated April 11, 1972 Inventor-(s) Hans=Ferdi Fink etq, ale

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the grant (only) cancel the sheet of drawing Signed and sealed this 12th day of December 1972 (SEAL) Attest:

EDWARD MGFLETCHERJR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMM-DC 6O376-F'69 & us. GDVERNMENY PRINTING OFFICE: I969 0-3e6-3am Patent NO. 3,555,554 Dated April 11,1972

Inventor(s) Hans -Ferdi Fink etc, 8.1,,

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the grant (only) cancel the sheet of drawing Signed and sealed this 12th day of December 1972;.

(EEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM Po-1oso (10-69) USCOMM-DC 60376-P69 u.s. GOVERNMENT PRINTING OFFICE I969 0-356-334. 

2. In an aqueous fire extinguishing composition, wherein the composition comprises a surface active substance, capable of being foamed into a fire fighting foam, the improvement which comprises that the aqueous composition contains between about 1 to 10% of finely dispersed silica.
 3. The improvement as claimed in claim 2, wherein said silica is colloidally dissolved in the water.
 4. The improvement as claimed in claim 3, wherein said silica contains OH-groups.
 5. In a method of combatting fire, wherein a liquid containing surface active substance is foamed and the foam is applied to the fire, the improvement which comprises that about 1 - 10 percent by weight of silica in fine particle form is added to the liquid or the foam. 